1. Field of the Invention
The present invention relates to a variable electrical energy stabilizer driven by a pulsation energy source having voltage amplitude varying in a constant ratio with the pulsation frequency, for supplying a d.c. output current to a load having a predetermined impedance.
2. Description of the Prior Art
Generally speaking, the input energy for a load stabilizer comes from a variable energy source, such as a variable voltage generator of the variable speed alternator type or a wind or solar generator. The input energy can also be delivered from an energy storage device; in particular, reference is made hereinafter to a reversible kinetic energy accumulator (KEA) which stores kinetic energy in a rotor whilst the rotor is driven by an alternating electrical generator. Should there be a failure in the main circuit normally feeding the electrical generator, the reversible feature of the kinetic energy accumulator enables it to function as an electrical generator, thus providing a certain lapse of time for supplying and triggering a stand-by electrical generator. Such kinetic energy accumulators are intended for supplying, for instance, a telephone exchange or an electrical unit at a sealed off site, e.g., a radio relay or station.
In a telephone exchange, the kinetic energy accumulator thus replaces the traditional electrochemical accumulators delivering a d.c. voltage of around 48 to 50 Volts. Means must be connected to the output of the kinetic energy accumulator for the purpose of stabilizing the electrical energy delivered from the kinetic energy accumulator. When the main circuit initially fails the kinetic energy accumulator is rotating at a high speed imparted to it by the associated alternating electrical generator. As the failure continues the kinetic energy of the accumulator is reduced, causing the voltage applied by the accumulator to a load to progressively drop. The dropping voltage is constantly proportional to the decreasing rotation speed of the accumulator rotor. The voltage applied to the load therefore varies in frequency and amplitude so much so that kinetic energy accumulator installations have generally included stabilizers which transform the variable frequency and amplitude voltage into a continuous energy. To provide the best possible efficiency the stabilizers usually derive a constant amplitude.
A known variable electrical energy stabilizer comprises a rectifier for rectifying the a.c. voltage that is supplied by the kinetic energy accumulator, and a continuous-continuous chopping voltage converter for stabilizing the rectifier voltage. The drawback, however, in this solution resides in the implementation of electronic circuits which comprise a large number of components, thereby diminishing the reliability of the stabilizer and generating steep-side currents that give rise to electromagnetic disturbances likely to perturb telephone signal transmission.